add a Buffer implementation that uses a buffer pool.

LICENSE-BSD

+### Applies to buffer.go and buffer_test.go ###
+
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

buffer.go

+// This is a derivitive work of Go's bytes.Buffer implementation.
+//
+// Originally copyright 2009 The Go Authors. All rights reserved.
+//
+// Modifications copyright 2018 Steven Allen. All rights reserved.
+//
+// Use of this source code is governed by both a BSD-style and an MIT-style
+// license that can be found in the LICENSE_BSD and LICENSE files.
+
+package pool
+
+import (
+	"io"
+)
+
+// Buffer is a buffer like bytes.Buffer that:
+//
+// 1. Uses a buffer pool.
+// 2. Frees memory on read.
+//
+// If you only have a few buffers and read/write at a steady rate, *don't* use
+// this package, it'll be slower.
+//
+// However:
+//
+// 1. If you frequently create/destroy buffers, this implementation will be
+//    significantly nicer to the allocator.
+// 2. If you have many buffers with bursty traffic, this implementation will use
+//    significantly less memory.
+type Buffer struct {
+	// Pool is the buffer pool to use. If nil, this Buffer will use the
+	// global buffer pool.
+	Pool *BufferPool
+
+	buf  []byte
+	rOff int
+
+	// Preallocated slice for samll reads/writes.
+	// This is *really* important for performance and only costs 8 words.
+	bootstrap [64]byte
+}
+
+// NewBuffer constructs a new buffer initialized to `buf`.
+// Unlike `bytes.Buffer`, we *copy* the buffer but don't reuse it (to ensure
+// that we *only* use buffers from the pool).
+func NewBuffer(buf []byte) *Buffer {
+	b := new(Buffer)
+	if len(buf) > 0 {
+		b.buf = b.getBuf(len(buf))
+		copy(b.buf, buf)
+	}
+	return b
+}
+
+// NewBufferString is identical to NewBuffer *except* that it allows one to
+// initialize the buffer from a string (without having to allocate an
+// intermediate bytes slice).
+func NewBufferString(buf string) *Buffer {
+	b := new(Buffer)
+	if len(buf) > 0 {
+		b.buf = b.getBuf(len(buf))
+		copy(b.buf, buf)
+	}
+	return b
+}
+
+func (b *Buffer) grow(n int) int {
+	wOff := len(b.buf)
+	bCap := cap(b.buf)
+
+	if bCap >= wOff+n {
+		b.buf = b.buf[:wOff+n]
+		return wOff
+	}
+
+	bSize := b.Len()
+
+	minCap := 2*bSize + n
+
+	// Slide if cap >= minCap.
+	// Reallocate otherwise.
+	if bCap >= minCap {
+		copy(b.buf, b.buf[b.rOff:])
+	} else {
+		// Needs new buffer.
+		newBuf := b.getBuf(minCap)
+		copy(newBuf, b.buf[b.rOff:])
+		b.returnBuf()
+		b.buf = newBuf
+	}
+
+	b.rOff = 0
+	b.buf = b.buf[:bSize+n]
+	return bSize
+}
+
+func (b *Buffer) getPool() *BufferPool {
+	if b.Pool == nil {
+		return GlobalPool
+	}
+	return b.Pool
+}
+
+func (b *Buffer) returnBuf() {
+	if cap(b.buf) > 0 && &b.buf[:1][0] != &b.bootstrap[0] {
+		b.getPool().Put(b.buf)
+	}
+	b.buf = nil
+}
+
+func (b *Buffer) getBuf(n int) []byte {
+	if n <= len(b.bootstrap) {
+		return b.bootstrap[:n]
+	}
+	return b.getPool().Get(n)
+}
+
+// Len returns the number of bytes that can be read from this buffer.
+func (b *Buffer) Len() int {
+	return len(b.buf) - b.rOff
+}
+
+// Cap returns the current capacity of the buffer.
+//
+// Note: Buffer *may* re-allocate when writing (or growing by) `n` bytes even if
+// `Cap() < Len() + n` to avoid excessive copying.
+func (b *Buffer) Cap() int {
+	return cap(b.buf)
+}
+
+// Bytes returns the slice of bytes currently buffered in the Buffer.
+//
+// The buffer returned by Bytes is valid until the next call grow, truncate,
+// read, or write. Really, just don't touch the Buffer until you're done with
+// the return value of this function.
+func (b *Buffer) Bytes() []byte {
+	return b.buf[b.rOff:]
+}
+
+// String returns the string representation of the buffer.
+//
+// It returns `<nil>` the buffer is a nil pointer.
+func (b *Buffer) String() string {
+	if b == nil {
+		return "<nil>"
+	}
+	return string(b.buf[b.rOff:])
+}
+
+// WriteString writes a string to the buffer.
+//
+// This function is identical to Write except that it allows one to write a
+// string directly without allocating an intermediate byte slice.
+func (b *Buffer) WriteString(buf string) (int, error) {
+	wOff := b.grow(len(buf))
+	return copy(b.buf[wOff:], buf), nil
+}
+
+// Truncate truncates the Buffer.
+//
+// Panics if `n > b.Len()`.
+//
+// This function may free memory by shrinking the internal buffer.
+func (b *Buffer) Truncate(n int) {
+	if n < 0 || n > b.Len() {
+		panic("truncation out of range")
+	}
+	b.buf = b.buf[:b.rOff+n]
+	b.shrink()
+}
+
+// Reset is equivalent to Truncate(0).
+func (b *Buffer) Reset() {
+	b.returnBuf()
+	b.rOff = 0
+}
+
+// ReadByte reads a single byte from the Buffer.
+func (b *Buffer) ReadByte() (byte, error) {
+	if b.rOff >= len(b.buf) {
+		return 0, io.EOF
+	}
+	c := b.buf[b.rOff]
+	b.rOff++
+	return c, nil
+}
+
+// WriteByte writes a single byte to the Buffer.
+func (b *Buffer) WriteByte(c byte) error {
+	wOff := b.grow(1)
+	b.buf[wOff] = c
+	return nil
+}
+
+// Grow grows the internal buffer such that `n` bytes can be written without
+// reallocating.
+func (b *Buffer) Grow(n int) {
+	wOff := b.grow(n)
+	b.buf = b.buf[:wOff]
+}
+
+// Next is an alternative to `Read` that returns a byte slice instead of taking
+// one.
+//
+// The returned byte slice is valid until the next read, write, grow, or
+// truncate.
+func (b *Buffer) Next(n int) []byte {
+	m := b.Len()
+	if m < n {
+		n = m
+	}
+	data := b.buf[b.rOff : b.rOff+n]
+	b.rOff += n
+	return data
+}
+
+// Write writes the byte slice to the buffer.
+func (b *Buffer) Write(buf []byte) (int, error) {
+	wOff := b.grow(len(buf))
+	return copy(b.buf[wOff:], buf), nil
+}
+
+// WriteTo copies from the buffer into the given writer until the buffer is
+// empty.
+func (b *Buffer) WriteTo(w io.Writer) (int64, error) {
+	if b.rOff < len(b.buf) {
+		n, err := w.Write(b.buf[b.rOff:])
+		b.rOff += n
+		if b.rOff > len(b.buf) {
+			panic("invalid write count")
+		}
+		b.shrink()
+		return int64(n), err
+	}
+	return 0, nil
+}
+
+// TODO: implement ReadFrom
+
+// Read reads at most `len(buf)` bytes from the internal buffer into the given
+// buffer.
+func (b *Buffer) Read(buf []byte) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	if b.rOff >= len(b.buf) {
+		return 0, io.EOF
+	}
+	n := copy(buf, b.buf[b.rOff:])
+	b.rOff += n
+	b.shrink()
+	return n, nil
+}
+
+func (b *Buffer) shrink() {
+	l := b.Len()
+	if l == 0 {
+		b.returnBuf()
+		b.rOff = 0
+	} else if l*8 < b.Cap() {
+		// Only shrink when capacity > 8x length. Avoids shrinking too aggressively.
+		newBuf := b.getBuf(l)
+		copy(newBuf, b.buf[b.rOff:])
+		b.returnBuf()
+		b.rOff = 0
+		b.buf = newBuf[:l]
+	}
+}

buffer_test.go

+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Modified by stebalien, 2018
+
+package pool
+
+import (
+	"bytes"
+	"io"
+	"math/rand"
+	"runtime"
+	"testing"
+)
+
+const N = 10000      // make this bigger for a larger (and slower) test
+var data string      // test data for write tests
+var testBytes []byte // test data; same as data but as a slice.
+
+func init() {
+	testBytes = make([]byte, N)
+	for i := 0; i < N; i++ {
+		testBytes[i] = 'a' + byte(i%26)
+	}
+	data = string(testBytes)
+}
+
+// Verify that contents of buf match the string s.
+func check(t *testing.T, testname string, buf *Buffer, s string) {
+	bytes := buf.Bytes()
+	str := buf.String()
+	if buf.Len() != len(bytes) {
+		t.Errorf("%s: buf.Len() == %d, len(buf.Bytes()) == %d", testname, buf.Len(), len(bytes))
+	}
+
+	if buf.Len() != len(str) {
+		t.Errorf("%s: buf.Len() == %d, len(buf.String()) == %d", testname, buf.Len(), len(str))
+	}
+
+	if buf.Len() != len(s) {
+		t.Errorf("%s: buf.Len() == %d, len(s) == %d", testname, buf.Len(), len(s))
+	}
+
+	if string(bytes) != s {
+		t.Errorf("%s: string(buf.Bytes()) == %q, s == %q", testname, string(bytes), s)
+	}
+}
+
+// Fill buf through n writes of string fus.
+// The initial contents of buf corresponds to the string s;
+// the result is the final contents of buf returned as a string.
+func fillString(t *testing.T, testname string, buf *Buffer, s string, n int, fus string) string {
+	check(t, testname+" (fill 1)", buf, s)
+	for ; n > 0; n-- {
+		m, err := buf.WriteString(fus)
+		if m != len(fus) {
+			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fus))
+		}
+		if err != nil {
+			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
+		}
+		s += fus
+		check(t, testname+" (fill 4)", buf, s)
+	}
+	return s
+}
+
+// Fill buf through n writes of byte slice fub.
+// The initial contents of buf corresponds to the string s;
+// the result is the final contents of buf returned as a string.
+func fillBytes(t *testing.T, testname string, buf *Buffer, s string, n int, fub []byte) string {
+	check(t, testname+" (fill 1)", buf, s)
+	for ; n > 0; n-- {
+		m, err := buf.Write(fub)
+		if m != len(fub) {
+			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fub))
+		}
+		if err != nil {
+			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
+		}
+		s += string(fub)
+		check(t, testname+" (fill 4)", buf, s)
+	}
+	return s
+}
+
+func TestNewBuffer(t *testing.T) {
+	buf := NewBuffer(testBytes)
+	check(t, "NewBuffer", buf, data)
+}
+
+func TestNewBufferString(t *testing.T) {
+	buf := NewBufferString(data)
+	check(t, "NewBufferString", buf, data)
+}
+
+// Empty buf through repeated reads into fub.
+// The initial contents of buf corresponds to the string s.
+func empty(t *testing.T, testname string, buf *Buffer, s string, fub []byte) {
+	check(t, testname+" (empty 1)", buf, s)
+
+	for {
+		n, err := buf.Read(fub)
+		if n == 0 {
+			break
+		}
+		if err != nil {
+			t.Errorf(testname+" (empty 2): err should always be nil, found err == %s", err)
+		}
+		s = s[n:]
+		check(t, testname+" (empty 3)", buf, s)
+	}
+
+	check(t, testname+" (empty 4)", buf, "")
+}
+
+func TestBasicOperations(t *testing.T) {
+	var buf Buffer
+
+	for i := 0; i < 5; i++ {
+		check(t, "TestBasicOperations (1)", &buf, "")
+
+		buf.Reset()
+		check(t, "TestBasicOperations (2)", &buf, "")
+
+		buf.Truncate(0)
+		check(t, "TestBasicOperations (3)", &buf, "")
+
+		n, err := buf.Write([]byte(data[0:1]))
+		if n != 1 {
+			t.Errorf("wrote 1 byte, but n == %d", n)
+		}
+		if err != nil {
+			t.Errorf("err should always be nil, but err == %s", err)
+		}
+		check(t, "TestBasicOperations (4)", &buf, "a")
+
+		buf.WriteByte(data[1])
+		check(t, "TestBasicOperations (5)", &buf, "ab")
+
+		n, err = buf.Write([]byte(data[2:26]))
+		if n != 24 {
+			t.Errorf("wrote 25 bytes, but n == %d", n)
+		}
+		check(t, "TestBasicOperations (6)", &buf, string(data[0:26]))
+
+		buf.Truncate(26)
+		check(t, "TestBasicOperations (7)", &buf, string(data[0:26]))
+
+		buf.Truncate(20)
+		check(t, "TestBasicOperations (8)", &buf, string(data[0:20]))
+
+		empty(t, "TestBasicOperations (9)", &buf, string(data[0:20]), make([]byte, 5))
+		empty(t, "TestBasicOperations (10)", &buf, "", make([]byte, 100))
+
+		buf.WriteByte(data[1])
+		c, err := buf.ReadByte()
+		if err != nil {
+			t.Error("ReadByte unexpected eof")
+		}
+		if c != data[1] {
+			t.Errorf("ReadByte wrong value c=%v", c)
+		}
+		c, err = buf.ReadByte()
+		if err == nil {
+			t.Error("ReadByte unexpected not eof")
+		}
+	}
+}
+
+func TestLargeStringWrites(t *testing.T) {
+	var buf Buffer
+	limit := 30
+	if testing.Short() {
+		limit = 9
+	}
+	for i := 3; i < limit; i += 3 {
+		s := fillString(t, "TestLargeWrites (1)", &buf, "", 5, data)
+		empty(t, "TestLargeStringWrites (2)", &buf, s, make([]byte, len(data)/i))
+	}
+	check(t, "TestLargeStringWrites (3)", &buf, "")
+}
+
+func TestLargeByteWrites(t *testing.T) {
+	var buf Buffer
+	limit := 30
+	if testing.Short() {
+		limit = 9
+	}
+	for i := 3; i < limit; i += 3 {
+		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, testBytes)
+		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(data)/i))
+	}
+	check(t, "TestLargeByteWrites (3)", &buf, "")
+}
+
+func TestLargeStringReads(t *testing.T) {
+	var buf Buffer
+	for i := 3; i < 30; i += 3 {
+		s := fillString(t, "TestLargeReads (1)", &buf, "", 5, data[0:len(data)/i])
+		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
+	}
+	check(t, "TestLargeStringReads (3)", &buf, "")
+}
+
+func TestLargeByteReads(t *testing.T) {
+	var buf Buffer
+	for i := 3; i < 30; i += 3 {
+		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
+		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
+	}
+	check(t, "TestLargeByteReads (3)", &buf, "")
+}
+
+func TestMixedReadsAndWrites(t *testing.T) {
+	var buf Buffer
+	s := ""
+	for i := 0; i < 50; i++ {
+		wlen := rand.Intn(len(data))
+		if i%2 == 0 {
+			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, data[0:wlen])
+		} else {
+			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testBytes[0:wlen])
+		}
+
+		rlen := rand.Intn(len(data))
+		fub := make([]byte, rlen)
+		n, _ := buf.Read(fub)
+		s = s[n:]
+	}
+	empty(t, "TestMixedReadsAndWrites (2)", &buf, s, make([]byte, buf.Len()))
+}
+
+func TestNil(t *testing.T) {
+	var b *Buffer
+	if b.String() != "<nil>" {
+		t.Errorf("expected <nil>; got %q", b.String())
+	}
+}
+
+/*
+func TestReadFrom(t *testing.T) {
+	var buf Buffer
+	for i := 3; i < 30; i += 3 {
+		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
+		var b Buffer
+		b.ReadFrom(&buf)
+		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(data)))
+	}
+}
+*/
+
+func TestWriteTo(t *testing.T) {
+	var buf Buffer
+	for i := 3; i < 30; i += 3 {
+		s := fillBytes(t, "TestWriteTo (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
+		var b Buffer
+		buf.WriteTo(&b)
+		empty(t, "TestWriteTo (2)", &b, s, make([]byte, len(data)))
+	}
+}
+
+func TestNext(t *testing.T) {
+	b := []byte{0, 1, 2, 3, 4}
+	tmp := make([]byte, 5)
+	for i := 0; i <= 5; i++ {
+		for j := i; j <= 5; j++ {
+			for k := 0; k <= 6; k++ {
+				// 0 <= i <= j <= 5; 0 <= k <= 6
+				// Check that if we start with a buffer
+				// of length j at offset i and ask for
+				// Next(k), we get the right bytes.
+				buf := NewBuffer(b[0:j])
+				n, _ := buf.Read(tmp[0:i])
+				if n != i {
+					t.Fatalf("Read %d returned %d", i, n)
+				}
+				bb := buf.Next(k)
+				want := k
+				if want > j-i {
+					want = j - i
+				}
+				if len(bb) != want {
+					t.Fatalf("in %d,%d: len(Next(%d)) == %d", i, j, k, len(bb))
+				}
+				for l, v := range bb {
+					if v != byte(l+i) {
+						t.Fatalf("in %d,%d: Next(%d)[%d] = %d, want %d", i, j, k, l, v, l+i)
+					}
+				}
+			}
+		}
+	}
+}
+
+var readBytesTests = []struct {
+	buffer   string
+	delim    byte
+	expected []string
+	err      error
+}{
+	{"", 0, []string{""}, io.EOF},
+	{"a\x00", 0, []string{"a\x00"}, nil},
+	{"abbbaaaba", 'b', []string{"ab", "b", "b", "aaab"}, nil},
+	{"hello\x01world", 1, []string{"hello\x01"}, nil},
+	{"foo\nbar", 0, []string{"foo\nbar"}, io.EOF},
+	{"alpha\nbeta\ngamma\n", '\n', []string{"alpha\n", "beta\n", "gamma\n"}, nil},
+	{"alpha\nbeta\ngamma", '\n', []string{"alpha\n", "beta\n", "gamma"}, io.EOF},
+}
+
+func TestGrow(t *testing.T) {
+	x := []byte{'x'}
+	y := []byte{'y'}
+	tmp := make([]byte, 72)
+	for _, startLen := range []int{0, 100, 1000, 10000, 100000} {
+		xBytes := bytes.Repeat(x, startLen)
+		for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
+			buf := NewBuffer(xBytes)
+			// If we read, this affects buf.off, which is good to test.
+			readBytes, _ := buf.Read(tmp)
+			buf.Grow(growLen)
+			yBytes := bytes.Repeat(y, growLen)
+			// Check no allocation occurs in write, as long as we're single-threaded.
+			var m1, m2 runtime.MemStats
+			runtime.ReadMemStats(&m1)
+			buf.Write(yBytes)
+			runtime.ReadMemStats(&m2)
+			if runtime.GOMAXPROCS(-1) == 1 && m1.Mallocs != m2.Mallocs {
+				t.Errorf("allocation occurred during write")
+			}
+			// Check that buffer has correct data.
+			if !bytes.Equal(buf.Bytes()[0:startLen-readBytes], xBytes[readBytes:]) {
+				t.Errorf("bad initial data at %d %d", startLen, growLen)
+			}
+			if !bytes.Equal(buf.Bytes()[startLen-readBytes:startLen-readBytes+growLen], yBytes) {
+				t.Errorf("bad written data at %d %d", startLen, growLen)
+			}
+		}
+	}
+}
+
+// Was a bug: used to give EOF reading empty slice at EOF.
+func TestReadEmptyAtEOF(t *testing.T) {
+	b := new(Buffer)
+	slice := make([]byte, 0)
+	n, err := b.Read(slice)
+	if err != nil {
+		t.Errorf("read error: %v", err)
+	}
+	if n != 0 {
+		t.Errorf("wrong count; got %d want 0", n)
+	}
+}
+
+// Tests that we occasionally compact. Issue 5154.
+func TestBufferGrowth(t *testing.T) {
+	var b Buffer
+	buf := make([]byte, 1024)
+	b.Write(buf[0:1])
+	var cap0 int
+	for i := 0; i < 5<<10; i++ {
+		b.Write(buf)
+		b.Read(buf)
+		if i == 0 {
+			cap0 = b.Cap()
+		}
+	}
+	cap1 := b.Cap()
+	// (*Buffer).grow allows for 2x capacity slop before sliding,
+	// so set our error threshold at 3x.
+	if cap1 > cap0*3 {
+		t.Errorf("buffer cap = %d; too big (grew from %d)", cap1, cap0)
+	}
+}
+
+func BenchmarkWriteByte(b *testing.B) {
+	const n = 4 << 10
+	b.SetBytes(n)
+	buf := NewBuffer(make([]byte, n))
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		for i := 0; i < n; i++ {
+			buf.WriteByte('x')
+		}
+	}
+}
+
+// From Issue 5154.
+func BenchmarkBufferNotEmptyWriteRead(b *testing.B) {
+	buf := make([]byte, 1024)
+	for i := 0; i < b.N; i++ {
+		var b Buffer
+		b.Write(buf[0:1])
+		for i := 0; i < 5<<10; i++ {
+			b.Write(buf)
+			b.Read(buf)
+		}
+	}
+}
+
+// Check that we don't compact too often. From Issue 5154.
+func BenchmarkBufferFullSmallReads(b *testing.B) {
+	buf := make([]byte, 1024)
+	for i := 0; i < b.N; i++ {
+		var b Buffer
+		b.Write(buf)
+		for b.Len()+20 < b.Cap() {
+			b.Write(buf[:10])
+		}
+		for i := 0; i < 5<<10; i++ {
+			b.Read(buf[:1])
+			b.Write(buf[:1])
+		}
+	}
+}